The present invention relates to an improved interference fit free floating ball valve for use in high pressure, high temperature environments, and more particularly, to an improved ball type valve wherein a pair of operating stems interconnect with slots on the ball valving member, to allow relative movement between the stems and the ball as the valve is moved between open and closed positions. The preferably extend externally of the housing so that the valve ball can be operated by either stem. A valve housing supports the free floating ball valving member therein, with each stem engaging a slot of the ball so that rotation of either stem rotates the valve. The stems and slots are sized so that an interference fit between the ball and the valve downstream floating seat is formed in the closed flow position. In the open position, a loose file allows field disassembly of the bonnet, stems and ball portions. The two stems are mounted within the housing on a common axis. A flexible annular guard skal prevents corrosion and erosion of the stem-to-ball connections.
Valves are often used in situations where high pressures, high temperatures or like severe conditions require a very tight or "interference" fit in which the valve closure member is biased into a force fit contact with a seat portion of the valve to thereby prevent leakage between the valve member and the valve body upon closure. This type of valve has particular utility, for example, in the geothermal and oil well industries.
The biasing of a valving member into an engaged "interference fit" position with a valve body (and more specifically with the valve seat of the body) is a broad concept which has been discussed in a number of U.S. patents. Notice, for example, U.S. Pat. Nos. 3,712,584 entitled "Valve and Method of Making Same" issued to Eugene Wise and Homer Galt. In that patent, a ball valving member is rotatably mounted within a valve body having inlet and outlet passages. The valve body is provided with one or more raised portions on its interior surface which serve to firmly engage or bias the valve member when it is rotated to the closed position, thereby preventing leakage between the valve member and the valve body during operation. In the manufacture of such a valve in accordance with the Wise et al patent, the body is formed of a suitable plastic material and is molded about the valve member. The valve member is placed in an open position in the mold and is provided with one or more recessed portions on the outer surface thereof so that complementary raised portions are formed on the inner surface of the molded valve body which serve to firmly engage or bias the valve member when it is rotated to a closed position. Unlike the present invention, a single stem rather than two stems is provided in Tirse et al. Further, Wise et al. does not have the free floating ball, operable by the stems which engage slots on the ball, allowing relative movement between the ball and stems. Further the flexible guard seal to protect the stem-to-ball connection is not seen.
Another ball valve having an interference fit or wedgeball member is the Behle et al. patent, U.S. Pat. No. 4,440,380. In the Behle patent, at least one ball valve segment is located within a partial valve cage mounted within a tank. The cage is integral with a valve housing removably mounted within a tank mounted flange. The housing includes an inclined sealing surface which the ball valve segment engages in closed position. A lading outlet chamber is located below the inclined seating surface. An operating shaft is inclined with respect to the outlet chamber. Inclined openings are provided in the valve housing and in the outlet chamber through which the operating shaft passes. The valve uses not two but one operating shaft that includes and eccentric head which is located within a non-round slot in the ball valve segment. Rotation of the operating shaft rotates the eccentric head which drives the valve segment between open and closed positions. Preferably a pair of ball valve segments located approximately 180.degree. apart are connected with supports or ribs. The valve segment which closes the opening into the discharge chamber is larger. The contour of the eccentric head is such that the smaller valve segment is located outwardly from the center of the discharge opening in the valve housing when the larger valve segment is in open position to minimize flow restriction. The smaller valve segment is cam shaped to urge the larger portion into closed and sealed position. This device doesn't use the dual stem, interference fit ball valve of the present invention using a free floating ball valve operable by either stem. Further, the housing and bonnet carrying separate stems which affords easy disassembly and easy access to the ball is not shown.
A ball type valve having a wedge or interference type fit can be seen in the patent to Graham, U.S. Pat. No. 3,941,351. Graham U.S. Pat. No. 3,941,351 patent shows a single stem that operates an otherwise free floating ball. The ball has an integrally attached hub that freely rotates within a circular recess of the valve body. The valve is closed by a quarter (1/4) turn rotation of the ball. A single stem or toggle purportedly serves a dual function of closing the ball and pressure sealing the ball after the ball is closed. The stem includes a lower end that fits into a matching groove on the core or ball valving member. A cam disc and sleeve cooperate with the stem or toggle to pivot the stem or toggle about an axis parallel to the targeted axis of the core or ball valving member in order to force the core or ball valving member against the valve seat. Graham differs from the present invention because only a single stem is used by Graham. In the present invention, two aligned stems are mounted for rotation in the valve body and these two stems each transmit load between the valve body and the free floating ball to produce an interference or force fit of the ball against a valve seat. An annular flexible seal protect the stem-to-ball connection.
A high pressure ball valve manufactured by W.K.M. Division, ACF Industries, Inc., P.O. Box 4334, Houston, Tex. 77210, is sold under the designation Dyna Seal 360 (API2000-5000 psi) and Dyna Seal 370 (Class 600-2500 psi). The Dyna Seal valve is high pressure ball valve using a one piece body with annular open top through which a ball and stem one piece assembly can be inserted. The Dyna Seal valve includes a bonnet that can be unbolted and removed. The one piece ball-stem-trunnion can then be pulled clear of the valve seats through the top of the valve body, permitting seat replacement. The Dyna Seal valve utilizes floating one piece metal seats with locked in place non-metallic face seals. In Dyna Seal valve, in order to obtain a seal at low pressure, a series of wave springs force the seats against the ball. However, at higher line pressures the upstream seat is forced against the ball by the pressure working across the differential area on the seat. Force from the springs becomes insignificant at these higher pressure ranges. The Dyna Seal 360, 370 class W.K.M. valves differ from the present invention because they do not show the free floating ball construction of the present invention which is operated by stems which are separate from the ball valving member. Rather, the W.K.M. Dyna Seal uses a one piece stem and ball assembly that does not permit relative movement between the ball and the two stems as is the case of the present invention. Further, the W.K.M. Dyna Seal valve does not produce an interference fit when the valve is rotated to a closed position by producing a change in relative movement between the stems and the ball between such open flow to closed flow positions. Further, the Dyna Seal valve does not have the flexible annular seal which conforms to the upstream upside of the ball valving member and flexs with it during operation to prevent corrosion of the stem-to-ball connection. Another problem with the W.K.M. Dyna Seal high pressure valve is that the integral ball and stem construction does not provide a free floating ball so that pressure can not be used to force the ball against the downstream seat in the closed position. While the W.K.M. high pressure Dyna Seal valve is a top entry valve, the ball is held in position with a series of wafer springs which require special tools to remove both seats from contact with the ball so that the ball can be removed for servicing. With the present invention, in line repairs can be quickly made with conventional tools such as socket wrenches. Since the interference fit is relieved when the valve is opened, the ball can be simply lifted from the housing (after the bonnet is disassembled) with a screw driver or the like. Thus, the present invention is a paragon of simplicity, having minimal parts, and corresponding ease of repair and maintenance.
W.K.M. Division, AFC Industries, Inc., also manufactures a 150 psi and 300 psi class ball valve under the designation "Dyna Seal 370" which uses a single stem operating ball valve. The stem-to-ball connection includes the use of a rectangular drive portion of the stem which interconnects with a slot on the ball valve. The Dyna Seal 370 valve differs from the present invention because a single rather than a dual stem construction is shown. Further, with the W.K.M. Dyna Seal 370, an interference fit is not produced on the downstream seat of the valve which is produced by load transferred through both stems from the valve body to the valving member and to the valve seat. Further, the W.K.M. 370 series valve does not use the flexible guard on the upstream side of the ball valving member to protect the stem-to-ball connections.
Both of the above discussed W.K.M. Dyna Seal valves use flanged ends which respectively have inlets and outlets and a longitudinal cylindrical bore with a linear central axis. However, the 150 and 300 class Dyna Seal 370 uses a two part valve housing unlike the single piece body or housing of the present invention with a bonnet wherein the housing carries one stem and the bonnet carries a separate stem, both of which are separate and moveable with respect to the ball valving member. This two part valve requires removal of the entire valve for repair, as in line repairs are not possible.